Source: Neilsen Co.

According to Nielsen’s latest Mobile Report, issued Monday, Apple AAPL has nearly caught up to Research in Motion RIMM in the U.S. smartphone market, with 28% and 30% of installed base, respectively. Google’s GOOG Android, with 19% is gaining fast.

“Among those who chose a device in the last six months,” Nielsen reports, “Android took the lead in Q3, while RIM Blackberry and Apple iPhone are practically tied for second place.”

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